Hiroko's sister Taeko recently committed suicide by jumping under a train. She was found clutching a piece of paper on which she had written a vow to return as a ghost and curse someone. However, the name is obscured by a blood stain, making it impossible to tell who the "will" was addressed to.
Hiroko is convinced that Taeko killed herself because of an argument they had on the night she died; Taeko had revealed that she was actually Hiroko's cousin, adopted as a baby after her parents died. Hiroko begins to have guilt-fuelled nightmares of Taeko as a ghost, remembering that their parents had always favored her even as she bullied Taeko when they were children.
Hiroko speaks to one of Taeko's friends to see if there was anyone else Taeko hated. The only possible other person is Keiko Yamada, a classmate who had transferred schools long ago. With this, the family is sure that Taeko had killed herself because she knew she was adopted.
Hiroko hears wailing coming from Taeko's room, and arrives in time to see Taeko's ghost in the room. She screams for her parents, who also see the ghost. The ghost returns on other nights and the family hears the sound of her searching for something in the attic. During this time, Hiroko also discovers that Keiko Yamada had told Taeko she was adopted.
Eventually, the family tries to apologise to Taeko's ghost, but she only screams "Where is it? Where is it?" and disappears, reappearing upstairs to look for something. This time, Hiroko is not convinced the ghost is really Taeko, pointing out that the blood covering her makes it difficult to tell who she really is. At this point, Keiko Yamada's father calls on the family, saying that there is a ghost at his house that he believes to be Taeko. He claims that she is searching for Keiko, but Keiko is not there - she had jumped under a train on the same night as Taeko, due to the failure of her father's business. She was found clutching a will in which she promised to return as a ghost and curse Taeko.
At that moment, the ghost appears in front of Mr. Yamada. Recognizing her as Keiko, he tells her to rest in peace because Taeko is no longer in this world. The ghost disappears, and neither she nor Taeko is ever seen again. Hiroko reflects on the irony of the girls' fate: both committed suicide on the same night, by the same method, and each left a will promising to curse the other. She believes they still hate each other in the next world.